PHILADELPHIA (CBS) – Dozens of people took advantage of free HIV testing in Philadelphia Sunday for World AIDS Day, but advocates are concerned that some of those most at risk are still not taking precautions.

“The test is easy — just a swab of the mouth and it’s better safe than sorry,” Don Acosta says.

Acosta is one of the nearly 100 people who ended years of procrastination by getting tested in a day-long event at the Chosen 300 Ministry on Spring Garden Street.

“My test came out negative and I’m glad to know that,” he said.

Chosen 300 partnered with its neighbor, AIDS prevention group Bebashi, to administer tests to the homeless men it serves.

The prevalence of AIDS among the homeless is three times higher than in the general population, so they’re an important target for testing, but Bebashi supervisor Jannah Myers remains concerned about another group who did not show up for the free testing.

“We have a high rate of contracting the disease between 14 and 18,” Myers said.

Myers says teenagers not only seem oblivious to the risk, they rarely seek testing.